Abstract
Herein, a label-free colorimetric nanosensor for Hg(II) is developed utilizing the hindering effect of Hg(II) on the kinetic aspect of gold nanoparticle (AuNPs) growth on the surface of gold nanostars (AuNSs). H-AuNS probes are synthesized and modified by 2-[4-(2-hydroxyethel) piperazine-1-yl] ethanesulfonic acid (HEPES). After the formulation of the reagents and testing conditions are optimized, HEPES-capped AuNSs (H-AuNSs) demonstrates good selectivity and sensitivity towards Hg(II) determination. A H-AuNS probe, in the presence of HCl/Au(III)/H2O2, is capable of detecting a Hg(II) concentration range of 1.0 nM–100 µM, with a detection limit of 0.7 nM, at a signal-to-noise ratio of 3.0, and a visual detection limit of 10 nM with naked eyes. For practicality, the H-AuNS probe is evaluated by measuring Hg(II) in the environmental water matrices (lake water and seawater) by a standard addition and recovery study. The detection limits for environmental samples are found to be higher than the lab samples, but they are still within the maximum allowable Hg concentration in drinking water (10 nM) set by the US Environmental Protection Agency (EPA). To create a unique nanosensor, the competitive interaction between Hg(II) and Pt(IV) toward the H-AuNSs probe is developed into a logic gate, improving the specificity in the detection of Hg(II) ions in water samples.
Highlights
The environmental conservation of fresh water resources and the efforts to protect fresh water from hazardous contaminants have become a primary priority in many countries
HEPES-capped AuNSs (H-AuNSs) were prepared by the reduction of gold chloride in a HEPES buffer at room temperature [18]
H-AuNSs solution, Au(III) ions were adsorbed onto the H-AuNS surface from electrostatic interactions between Au(III) and the negatively charged HEPES on the H-AuNS surface [32]
Summary
The environmental conservation of fresh water resources and the efforts to protect fresh water from hazardous contaminants have become a primary priority in many countries. Hg(II) determination, such as atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), stripping voltammetry, and polarography [5,6,7]. These analytical methods offer advantages in terms of good stability, selectivity, sensitivity, and legal acceptability as the national standard detection methods for many countries. The drawbacks of these methods include bulky instrumentation, high cost per analysis, long analysis time, stringent requirements of sample storage, highly trained personnel, and relatively expensive instruments, which thereby limits their use for fast Hg(II) monitoring in the field. A portable, facile, rapid, and low cost colorimetric method for Hg(II) detection is needed
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